Tiel tobnblom



E. A. E. TRNBLOM.

ELECTRIC HEGULATING RESISTANCE.

APNIC/mon FILED oc. 14. 19m.

1,306,085, Patented June 10, 1919.

UNITED STATES PATENT OFFICE.

EnNsT ALBERT MANUEL TnNELom. oF EsxILsTUNA. SWEDEN.

' ELECTRIC EEGULATING RESISTANCE.

Specification of Letters Patent.

Patented June 1o, 1919.

Application leld'October 14, 1918. Serial No. 258,090.

ing at Eskilstuna, Sweden, have invented certain new, and useful Improvements in Electric Regulatin Resistances, of which the following is a ll, clear, vand exact description.V l y j My invention *relates to suchelectric regulating resistances in which the resistance 1n an electric circuit may be varied continually i by means of nearing two elastic contacts-surfaces toward each other or by; removing them from each other. The invention is especially intended to be used for varying the current-or the voltage in secondary mains and more particularly in electric 'l Welding and the like, but it may also be used for other purposes, especially when a uniform variation of the resistance is re- 1 quired.

In the following description of the invention reference is made of the accompanying drawing, in which a form of the invention used for Welding purposes or the like is illustrated.

Referring to the drawing 1 represents the primary coilg-"Q the iron core and 3 the secondary coil. In the circuit of the latter a resistance is placed consisting in aknown way of two lelastic elements 4' electrically connected with each other at one end. The two surfaces of these elements facing each other are plane when they are in contact with each other along their entire length. The elements 4 are, at one end 5, connected with each other b f meansof screws or the like and they are normally separated from each other on the length by being bent outward from each other. One (or both) of the oppositeends of the elements is connected with means for bringing these ends together and for separating them again. This device consists, in the form shown in the drawing, of a lever 6 pivoted at 7 and connected at one end by means of a rod 8 with the end of one of the resistance elements 4 while the end of the other element is connected with the part of the secondary mains that is intended to support the working piece to be welded. On the secondary coil conducting springs 9 are provided which allow a certain movement of the parts of the'apparatus, and one of ments 4 are remainlng part of their' all amounts of resistance between O and a maximum value can be obtained by one single manipulation.

In order to reduce the contact resistance as much as possible, when the Current passes the surfaces of the elements 4 touching each other a band or a tongue 10 of another material is placed between the two elements 4 according to the present invention. This tonguemay consists of copper if `the elemade of iron, and it is placed 1n such away that one of its ends 1s fastened at 5 while its other end projects freely -between thcv elements 4. When these latter are caused to approach each other the current must pass through the intermediate tongue 10 that is brought into contact with them both more and more.

As the resistance elements 4 must be tempered or hardened in order to effect a certain pressure-at the contact and still be able to resume their original form, they will be little apt to come into a very close contact with each other, z'. e'., to offer a small resistance to the current. On the other hand the tongue l0, being made of copper or the like and thus comparatively soft, will follow the contact surfaces very closely and offer only a minimum of resistanceto the current. It is also a good heat conductor and thus it abstracts very well the heat generated.

It is obvious that a resistance provided with a tongue of this type is able to stand much greater loads than a resistance without such a tongue and this is also shown by experiments.

While I have confined my description to but one form for applying the invention, it, of course, will be understood that it may be varied in several ways without departin from the spirit of my 1nvention, all of whic is included in the appended claim.

What I claim as new is:`

An electric regulating resistance comprising elastic elements with surfaces of contact facing each other and at one end connected with each other, the opposite ends being In testimony whereof I have signed my connected with an electric circnt, a. tongue, name to this specification Ain the presence of fofan'other materialthan the elements, at one two Subscribing witnesses. l end fastened between the ends of sald reslst- ERNST ALBERT EMANUEL 'I'ORNBLOM ance elements where these are connected Witnesses: y with each otherand'atthe opposite end pro` KARL Y. SWANSON, jecting freely between saidy elastic elements. GRETA PRIEN. 

